The Lexical Verbs 'Be' And 'Have'

Halliday & Matthiessen (2014: 153):

There are two lexical verbs in English, be and have, where, strictly speaking, the simple past and simple present forms consist of Finite element only, rather than of a fusion of Finite with Predicator. This is shown by the negatives: the negative of is, was is isn’t, wasn’t – not doesn’t be, didn’t be. Similarly with have (in the sense of ‘possess’, not have in the sense of ‘take’): the negative forms are hasn’t, hadn’t. The pattern with have varies with the dialect: some speakers treat have ‘possess’ just like have ‘take’, with negative doesn’t have; others expand it as have + got (cf. I haven’t a clue / I don’t have a clue / I haven’t got a clue). But since in all other tenses be and have function as Predicators in the normal way, it seems simpler to analyse them regularly, as ‘(past/present) + be/have’.